【2½】负5次方 ×【0.25】5次方×【五分之二】负5次方×【负¼】负五次方
=（5/2)^(-5)*(1/4)^5*(2/5)*(-5)*(-1/4)^(-5)
=-(2/5)^5*(1/4）^5*(5/2)*5*4^5
=-[2/5*1/4*5/2*4]^5
=-1